The gentle touch that calms pets can be traced to a genetically single, genetically tractable neuron, researchers from the California Institute of Technology reported this week (January 30) in Nature.
Researchers have known that a specific subset of neurons, sometimes called CT afferents, were responsible for conveying pleasant or anxiety-producing senses. But no one had found the molecular marker for these nerves, nor been able to link them directly to behavior. By creating a window into a living mouse and genetically labeling the neurons they suspected were involved, researchers were able to see specific neurons light up when then mouse was stroked with a paintbrush.
In a second experiment, the researchers activated mice’s pleasant-touch nerves with a drug and placed them in a chamber with a specific smell and look. The investigators also injected the same mice with saline and placed them in an adjacent room with a different smell and look. After these training sessions, they let the mice choose between the two chambers and saw that the animals consistently favored the room in which they had associated with the positive touch sensation.
The findings “imply that social touch is not simply nice, but that it has calming power in the context of something less-than-wonderful,” India Morrison, a neuroscientist at the University of Gothenburg in Sweden, told ScienceNOW.